APEX

Hi Everyone. I have developed an APEX Application which will be accessed from a bigger application. For the sake of clarity lets call my application 'B' and bigger application A.

Here's the situation

1) User will log into Application A with a username/password.
2) Once successfully logged in, Application A will display a link to my application B.
3) Clicking on the link will open a new browser window with my application, but it should not prompt for username/password. Application A can pass username to Application B.
4) Application B is storing a list of users in a table. Application B will recieve the username from Application A and check in that table to make sure the user exists.
5) If user exists, let them use the application, otherwise deny.

So here are my questions.

1) First I need to understand how can application A pass a username to Application B. Lets say the actual weblink is

https://apex.app.com/apex/f?p=299

what else has to be added to the weblink above for application A to pass a username. Lets assume username will be stored in item P1_USERNAME. I will appreciate if you can provide the syntax..

2) What changes I have to make on the APEX Login page to not ask for username/password and still have my authroization (edit, view, admin) work.

Thanks for your suggestions. I am sure people have accomplished this in their applications. I will appreciate if you share.

Thanks